Mechanical circulatory assist devices are being developed for medium-term and long-term help to ambulatory patients with chronic heart failure, as well as for immediate temporary treatment of acute myocardial infarction and for postcardiotomy patients. In recent years there hash been increasing development of continuous flow blood pumps to replace pulsatile devices in circulatory assist. Purge liquid has been supplied successfully to lubricate the bearings and wash the seals that separate the blood and bearing compartments of implantable rotary blood pumps to minimize both hemolysis and thrombosis, extending the operating endurance of the pump. In animal tests to-date, such purge liquids have been applied from extracorporeal roller pumps through percutaneous tubes. There is a need for a wearable purge liquid system for short and intermediate term use with rotary blood pumps that are implanted in cardiac patients. A design has been generated for a miniature wearable reciprocating pump to deliver metered purge liquid to implanted rotary blood pumps. A program is presented for experimental evaluation of this design. PROPOSED COMMERCIAL APPLICATION: Improved implanted blood pumps for circulatory assist devices.